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A practical total synthesis of AK-toxins (AK-toxin I, 1 ; II, 2 ), host-specific toxins against the Japanese pear, has been achieved in 10% total yield, starting from the key intermediate 6 . The (2E,4Z,6E)-conjugated triene system was successfully constructed by the use of the Stille coupling reaction between the (E,Z)-bromodiene ( 17 ) and (E)-stannylacrylate ( 21 ). The (E,Z)-configuration of 17 was established with excellent geometrical purity by palladium-catalyzed stereoselective hydrogenolysis of gem-dibromide ( 15 ), which was derived from 6 via the Wittig–Horner reactions. |
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